Corner lock construction

Claim 1

IN A FRAME COMPRISED OF PLURALITY OF FRAME SECTIONS GENERALLY L-SHAPED IN TRANSVERSE CROSS SECTION, THE FRAME SECTIONS BEING FORMED TO DEFINE MITERED JOINTS, WITH ADJACENT ENDS OF A PAIR OF FRAME SECTIONS BEING INTERCONNECTED BY MEANS OF A CORNER LOCK, THE IMPROVEMENT COMPRISING AN IMPROVED CORNER LOCK CONSTRUCTION WHEREIN EACH FRAME SECTION HAS A PAIR OF FLANGES EXTENDNG OUTWARDLY FROM ONE LEG THEREOF, SAID FLANGES BEING PARALLEL TO ONE ANOTHER ALONG THE LENGTH OF EACH FRAME SECTION TO DEFINE A CHANNEL THEREBETWEEN, SAID CORNER LOCK BEING COMPRISED OF A PAIR OF ARMS EXTENDING PERPENDICULARLY TO ONE ANOTHER, EACH ARM BEING DISPOSED IN A CHANNEL OF AN ADJACENT FRAME SECTION, SAID CORNER LOCK BEING PROVIDED WITH SERRATIONS ALONG ONE SIDE OF EACH ARMS, MEANS DEFINING A RECESS IN EACH ARM OF THE CORNER LOCK, FIRST LUGMEANS COMPRISING A LOCKING LUG STRUCK FROM THE OUTERMOST ONE OF THE FLANGES ON EACH FRAME SECTION FOR ENGAGING WALL OF AN ASSOCIATED RECESS IN THE CORNER LOCK FOR DRAWING ADJACENT ENDS OF THE FRAME SECTIONS TOWARD ONE ANOTHER TO TIGHTLY JOIN ADJACENT ENDS OF THE FRAME SECTIONS IN ABUTTING RELATIONSHIP, AND SECOND LUG MEANS FORMED FROM THE FLANGES ON EACH FRAME SECTION FOR SECURING THE CORNER LOCK IN PLACE IN THE CHANNEL, SAID SECOND LUG MEANS COMPRISING PORTIONS STRUCK OUT FROM THE OUTERMOST FLANGE OF EACH FRAME SECTION AND HAVING COMPLEMENTARY SERRATION FOR ENGAGEMENT WITH THE SERRATIONS IN SAID CORNER LOCK AND OTHER PORTIONS STRUCK FROM THE INNERMOST FLANGE AND BENT INTO CLAMPING ENGAGEMENT WITH THE CORNER LOCK.